package com.banksoft.util;

public class DistanceUtil {
	
	   private final static double DEF_PI = 3.14159265359; // PI
	    private final static double DEF_PI180 = 0.01745329252; // PI/180.0
	    private final static double DEF_R = 6370693.5; // radius of earth
       static double DEF_2PI= 6.28318530712; // 2*PI
	
	public static double getLongDistance(double lon1, double lat1, double lon2, double lat2) {
        double ew1, ns1, ew2, ns2;
        double distance;
// 角度转换为弧度
        ew1 = lon1 * DEF_PI180;
        ns1 = lat1 * DEF_PI180;
        ew2 = lon2 * DEF_PI180;
        ns2 = lat2 * DEF_PI180;
// 求大圆劣弧与球心所夹的角(弧度)
        distance = Math.sin(ns1) * Math.sin(ns2) + Math.cos(ns1) * Math.cos(ns2) * Math.cos(ew1 - ew2);
// 调整到[-1..1]范围内，避免溢出
        if (distance > 1.0)
            distance = 1.0;
        else if (distance < -1.0)
            distance = -1.0;
// 求大圆劣弧长度
        distance = DEF_R * Math.acos(distance);
        return distance;
    }
	
	 public static double GetShortDistance(double lon1, double lat1, double lon2, double lat2)
     {
         double ew1, ns1, ew2, ns2;
         double dx, dy, dew;
         double distance;
         // 角度转换为弧度
         ew1 = lon1 * DEF_PI180;
         ns1 = lat1 * DEF_PI180;
         ew2 = lon2 * DEF_PI180;
         ns2 = lat2 * DEF_PI180;
         // 经度差
         dew = ew1 - ew2;
         // 若跨东经和西经180 度，进行调整
         if (dew > DEF_PI)
         dew = DEF_2PI - dew;
         else if (dew < -DEF_PI)
         dew = DEF_2PI + dew;
         dx = DEF_R * Math.cos(ns1) * dew; // 东西方向长度(在纬度圈上的投影长度)
         dy = DEF_R * (ns1 - ns2); // 南北方向长度(在经度圈上的投影长度)
         // 勾股定理求斜边长
         distance = Math.sqrt(dx * dx + dy * dy);
         return distance;
     }
	
	public static void main(String[] args){
        double x =  117.997525d;
        double y= 37.386753d;

        double x1 = 116.402419d;
        double y1 = 39.999398d;
        System.out.println("--------------  "+GetShortDistance(x1,y1,x,y));
    }
	
}
